By measuring the size of machine parts with universal measurement means, it is also necessary to consider surface roughness of the measurable machine parts. Large roughness is causing additional measurement errors. In particular important it is by the Nano technological surfaces of thin polythene. The theoretical calculations of the above mentioned error are covered in this paper. It is based on surface roughness model in random field form by using its normal distribution of regularities. In this case it may be verified, that for normal random field form described surface it is necessary to know only one parameter of roughness height and two different spacing parameters. Based on classical elasticity theory there are developed coherences which are linking measurement force with deformation of machine parts surface, what is reason of measurement error.